Variable resistance information reading element

ABSTRACT

A recording device in which there is added in accordance with a recording signal an impurity acting as a recombination center and forming a deep energy level to a solid like a semiconductor and an insulator having a forbidden band in their energy band structures and applying an elastic wave to said solid so that the electric resistance in the neighborhood of the impurity atoms is varied thereby converting the recorded signal to an electric signal.

United States Patent Inventors Akio Yamashita Ikeda-shi; Takehiro Tsuzaki, Osaka, all of Japan Appl. No. 752,294 Filed Aug. 13, 1968 Patented Nov. 23, 1971 Assignee Matsushita Electric Industrial Co., Ltd.

Osaka, Japan Priority Aug. 18, 1967 Japan 42/53366 VARIABLE RESISTANCE INFORMATION Primary Examiner-Stanley M. Urynowicz, Jr. Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: A recording device in which there is added in accordance with a recording signal an impurity acting as a READING ELEMENT recombination center and forming a deep energy level to a 5 Claims 2 Drawin Figs. solid like a semiconductor and an insulator havin a forbidden g b d h b d d 1 1 an m t err energy an structures an app ylng an e astlc US. Cl if/51;; :5; wave to said solid so that the electric resistance in the In Cl G1 1 H34 neighborhood of the impurity atoms is varied thereby conven- G M 13/02 mg the recorded signal to an electric signal. Field of Search 148/190, 186, 187; 340/173 MS, 174 MS; 333/30; 317/143, 144; 179/1002 PATENTEDNBV 23 l97| 3623025 INVENTORS HKIO nMnsM/m T KE/HI? Buzmr/ ATTORNEYS This invention relates to a recording device characterized in that a solid such as a semiconductor and an insulator having a forbidden band in their energy band structure has added an impurity acting as a recombination center and forming a deep energy level in the forbidden band depending on a recording signal.

Various recording devices such as a magnetic recorder, a sound recording disc, photograph and printing are used in various ways in different fields. Recently with the development of the information industry recording a large quantity of signals in a very small capacity has been increasingly required. Therefore, it is necessary to convert a very minute recording signal to a signal sensible to a machine or the human body accurately.

This invention provides an utterly new recording device different from that according to the conventional method. It is epoch-making that a large quantity of information is recorded in a capacity much smaller than a prior art one. The converted sensible signal is derived in various forms such as an electric signal, a light signal and a sound signal.

According to the research of the inventors, when an impurity forming a deep energy level and acting as a recombination center in the forbidden band is added to a solid such as a semiconductor and an insulator and an elastic wave is applied to the solid, a reversible strain appears in the vicinity of the impurity atoms decreasing the electric resistance therearound.

Therefore, if the addition of the impurity is made to follow the recording signal, the elastic wave yields a converted electric signal.

The invention will be understood by reference to the following description and the accompanying drawings in which:

FIG. 1 is a perspective view of a recording device embodying this invention; and

FIG. 2 is a diagram illustrating the manner in which an elastic wave propagates in the solid of the device.

The principle of the recording device of this invention will be explained next with reference to the drawings. FIG. I shows the principle and the structure of the recording device according to this invention. 1 is a semiconductor or an insulating solid having a forbidden band in the energy band structure. 2 shows a recording signal pattern formed in the solid 1 by the impurity which forms a deep energy level in the forbidden band and acts as a recombination center. 3 and 3' are solids having the piezoelectric property generating an elastic wave. 4, 5, 4 and 5' are electrodes fitted to the piezoelectric elements 3 and 3'. 6, 6', 6" and 6" are absorbing plates to eliminate the reflected waves. A and B are terminals connected to the electrodes 4 and 4 respectively and C is also a terminal connected to the electrodes 5 and 5. D and E (opposite side of D) are terminals led out of the solid 1.

Now when a voltage is applied across the terminals A and C, an elastic wave is generated in the piezoelectric solid 3 and propagates through the solid 1 as shown in FIG. 2. 7 and 8 are the elastic waves generated from the solids 3 and 3' respectively. 9 is the superposed elastic pulse wave at the intersection point P. The elastic pulse wave at P can scan the whole surface of the solid 1 by controlling the phase of the generated elastic wave.

Assume that the elastic wave at P reaches the position of the recorded signal 2 in FIG. 1. A reversible strain is then generated in the vicinity of the deep level impurity atoms, decreasing the electric resistance. Thus, in the presence of a voltage applied between the terminals D and E a current pulse is generated. This electric signal can be converted to either a television image or a print.

When the recording signal 2 follows an audio signal, it is sufficient that the waveform of the pattern 2 and the impurity concentration are varied in accordance with the audio signal. It is easy to convert the electric signal converted by the elastic wave to a sound. Therefore, this invention can provide a static type recorder without any movable portion and utterly distinct from a conventional tape recorder.

The addltion of the deep level impurity as the recording signal is made by ionizing and accelerating the impurity and radiating it to the solid 1.

The waveform or the signal pattern can be made by surface scanning of the ion beam. The light and shade of the signal pattern can be varied by the density of the ion beam and the acceleration energy.

In order to record the image only the photoetching technique may be applied to the surface of the solid 1 so that the image pattern formed by the impurity may diffuse into the solid 1 while heating. In this case, the fact that the deep level impurity has different diffusion coefficients depending on the crystals axes of the solid 1 is utilized to prevent fading of the pattern that might arise in the step of diffusion.

The solid may be made of well-known semiconductors such as Si, Ge, GaP, GaAs, InAs, AlN, LiNbO CdS, ZnS, ZnSe, CdSe, ZnO and SiC. These solids are preferably single crystals in view of noises and error signals.

The solid for generating the elastic wave is made of a piezoelectric element such as BaTiO quartz, CdS, GaAs etc. The existence of the plates for absorbing the reflected waves is desirable in order to eliminate the disturbance of the signal by the reflected waves. However, a suitable shape of the solid 1 can also accomplish the same purpose.

Next, an embodiment of this invention will be explained in detail.

Si semiconductor was used as the solid 1. Cu ion beam was scanned and radiated on the Si surface in accordance with the image signal so that Cu atoms were added to silicon. The beam spot was 25p.

A silicon crystal with the dimensions 20X20 mm. and a track length of 4 m was obtained. The ion beam density was varied and the speed of the pulse-type elastic wave was slowed down by the phase control. Thus, a recorder comparable with a conventional recording disc was formed. Sound signals were successfully recorded.

When the pattern of the ion beam is given as an image, the image signal can be recorded in a similar way.

Furthermore, if a PN junction or a Schottky barrier is formed in the solid 1 and the deep level impurity is added in the neighborhood of the junction, the sensitivity is promoted even with a low-output elastic wave.

As described above in detail, the recorder device of this invention based upon a new principle is small in size, without any movable portion, and can be applied to various usages. Therefore, theindustrial merit of this invention is very large.

What is claimed is:

1. A recording device comprising, in combination, a body of a material having a forbidden band in its energy band structure, said body having a deep energy level impurity distributed therein in accordance with a pattern of information recorded in said body; input and output means operatively connected with said body; and means producing a movable elastic wave pulse, including means propagating elastic waves in said body to produce said movable elastic wave pulse at the intersection point of said elastic waves, said propagating means being responsive to electric signal means applied to said input means.

2. A recording device as defined in claim 1, wherein said elastic wave propagating means comprises piezoelectric element means.

3. A recording device as defined in claim 2, wherein said piezoelectric element means comprises a material selected from the group consisting of BaTiO quartz, CdS and GaAs.

4. A recording device as defined in claim 1, wherein said body comprises a semiconductor material selected from the group consisting of Si, Ge, Gal, GaAs, lnAs, AlN, LiNbO CdS, ZnS, ZnSe, CdSe, ZnO and SiC.

5. A recording device as defined in claim 1, wherein said body comprises an insulating material. 

1. A recording device comprising, in combination, a body of a material having a forbidden band in its energy band structure, said body having a deep energy level impurity distributed therein in accordance with a pattern of information recorded in said body; input and output means operatively connected with said body; and means producing a movable elastic wave pulse, including means propagating elastic waves in said body to produce said movable elastic wave pulse at the intersection point of said elastic waves, said propagating means being responsive to electric signal means applied to said input means.
 2. A recording device as defined in claim 1, wherein said elastic wave propagating means comprises piezoelectric element means.
 3. A recording device as defined in claim 2, wherein said piezoelectric element means comprises a material selected from the group consisting of BaTiO3, quartz, CdS and GaAs.
 4. A recording device as defined in claim 1, wherein said body comprises a semiconductor material selected from the group consisting of Si, Ge, GaP, GaAs, InAs, A1N, LiNbO3, CdS, ZnS, ZnSe, CdSe, ZnO and SiC.
 5. A recording device as defined in claim 1, wherein said body comprises an insulating material. 